In 2011 the National Academy of Medicine convened a panel to explore the paradox of why the US spends more on healthcare than other Organization of Economic Cooperation and Development (OECD) countries yet has inferior outcomes. It concluded that ?Data are simply lacking to fully understand the causal factors responsible for each of the diseases and injuries that disproportionately affect the US population.? Although aggregate measures of health systems performance such as life expectancy and infant mortality rates suggest that US health care system performance lags, a limited number of direct comparisons of medical treatments suggest that the US may have better outcomes than OECD peers for acute conditions including hip fracture (HF) and acute myocardial infarction (AMI). Modestly improved US outcomes, however, come at the expense of extraordinarily high utilization of cardiac catheterization for AMI and other costly procedures. Moreover, disadvantaged populations in the US may fare worse than disadvantaged populations in other countries. It is a convenient narrative to simply conclude that the US spends more and gets less from an underperforming healthcare system. Yet, there may be a more nuanced story. Some research supports the notion that differences in where money is spent (acute care vs. social services) might explain part of the differences in health outcomes. Thus further rigorous research is needed to understand better the contributions of the health care system to outcomes. We propose to update a disjointed, incomplete and outdated literature by systematically studying patterns of utilization, outcomes, and treatment intensity for older adults with specific acute conditions treated in wealthy countries with vastly different healthcare systems. Our research will inform the debate about whether more intensive treatment practices in the US also lead to better outcomes. The overarching objective of our study is to compare treatment for older adults from five OECD countries (US, Canada, Netherlands, Israel and England) hospitalized with one of 5 carefully selected tracer conditions: hip fracture (HF), acute myocardial infarction (AMI); ischemic stroke, elective aortic aneurysm repair (AAA), and congestive heart failure (CHF). Our proposal has five specific aims that assess: (1) differences in the epidemiology of the conditions; (2) differences in treatment intensity; (3) differences in outcomes, including mortality at 90 days and one year; (4) differences after stratifying by socioeconomic status and overall health; and (5) differential changes in treatment patterns over time. Our proposed work will provide a nuanced understanding of the effectiveness of treatment approaches in the five countries and will provide insights into the functioning of their health care systems. The scientific premise of our proposal is that granular information is needed to inform the study of comparative health systems. In addition, the international collaboration that we form for this proposal will serve as the basis for developing research methods and expertise in using nationally representative data to compare healthcare across countries.